\begin{tikzpicture}
    \tkzDefPoints{0/0/B,  2.5/0/C, 0/1.5/A, 2.5/1.5/D}
    \tkzInterLL(A,C)(B,D)  \tkzGetPoint{O}
    \tkzDrawPolygon(A,B,C,D)
    \tkzDrawSegments(A,C  B,D)
    \tkzLabelPoints[left](A,B)
    \tkzLabelPoints[right](C,D)
    \tkzLabelPoints[above](O)
\end{tikzpicture}

